Amphibian aircraft



FIG. 1 is a front elevational view of an amphibian aircraft showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational view thereof, the opposite side elevational view being a mirror image thereof;

FIG. 4 is a top front perspective view thereof;

FIG. 5 is a rear elevational view thereof; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for an amphibian aircraft, as shown and described. 